The pelvic pain syndrome is a general term for pain diseases at the pelvic area and defined by the International Continence Society in 2002 as “the occurrence of persistent or recurrent episodic pelvic pain associated with symptoms suggestive of lower urinary tract, sexual, bowel or gynecological dysfunction, without proven infection or other obvious pathology” (cf. Non-patent Reference 1). The pelvic pain syndrome is classified into urological pain syndrome, gynecological pain syndrome, anorectal pain syndrome, neurological pain syndrome and muscular pain syndrome. The urological pain syndrome is further classified into bladder pain syndrome, urethral pain syndrome, penile pain syndrome, prostate pain syndrome and scrotal pain syndrome (cf. Non-patent Reference 2).
Non-bacterial chronic prostatitis is one of the urological pain syndrome and classified as the category III of the four classifications of prostatitis syndrome proposed in 1999 by National Institute of Health (NIH). The typical symptom of the non-bacterial chronic prostatitis is pain or discomfort at perineal, testicular and penile region and urinary symptoms such as a sensation of incomplete urine emptying and/or urinary frequency. Unlike the case of the acute bacterial prostatitis (category I prostatitis) and chronic bacterial prostatitis (category II prostatitis), a decisive therapeutic method for the non-bacterial chronic prostatitis has not been found because the etiology of the non-bacterial chronic prostatitis has been unclear. In comparison with other lower urinary tract diseases such as benign prostatic hyperplasia, interstitial cystitis and overactive bladder, the non-bacterial chronic prostatitis specifically induces male genital pain including testicular pain which is also mentioned in the chronic prostatitis symptom index of NIH (NIH-CPSI) (e.g., see Non-patent Reference 3).
Intraperitoneal administration of acetic acid-induced pain behavior (writhing) is generally used for evaluating the effect of analgesics (e.g., see Non-patent Reference 4).
Intravesical injection of acetic acid-induced bladder pain in rat (e.g., see Non-patent Reference 5), cyclophosphamide-induced bladder wall lesion resulting in cystitis in rat (e.g., see Non-patent Reference 6), a intravesical injection of acetone-induced irritable bladder dysfunction in Cercopithecus aethiops (e.g., see Non-patent Reference 7), a neurogenic cystitis which is induced injection of aujeszky's disease virus (pseudorabies virus) into the abductor caudalis dorsalis muscle in mouse (e.g., see Non-patent Reference 8), and intraprostatic injection of capsaicin-induced inflammation in the prostate gland with pain or discomfort behavior in rat (e.g., see Non-patent Reference 9) have been reported as animal model used for evaluating pain or discomfort derived from lower urinary tract.
On the other hand, it has been reported that hormone, stress, soybean-deficient/excess feeding, mechanical occlusion of the urethra and topical application of ethanol or DNBS into the prostate gland via urethra induced prostatitis in rodents (e.g., see Non-patent Reference 10).    Non-patent Reference 1: Urology, 2003, 61, p 37-49    Non-patent Reference 2: European Urology, 2004, 46, p 681-689    Non-patent Reference 3: Journal of Urology, 1999, 162, p 369-375    Non-patent Reference 4: Arzneimittal-Forschung Drug Research, 1975, 25 (10), p 1505-1509    Non-patent Reference 5: The Journal of Urology, 2004, 172, p 1529-1532    Non-patent Reference 6: The Journal of Urology, 2000, 164, p 203-208    Non-patent Reference 7: Neurourology & Urodynamics, 1995, 14 (6), p 657-665    Non-patent Reference 8: American Journal of Physiology Regulatory Integrative Comparative Physiology, 2007, 293, p 1191-1198    Non-patent Reference 9: European Urology, 2007, 51, p 1119-1127    Non-patent Reference 10: Prostate Cancer and Prostatic Diseases, 10, p 15-29